Satellite constellation having multiple orbital inclinations

ABSTRACT

A satellite system may have a constellation of communications satellites that provides services to users with electronic devices such as portable electronic devices and home and office equipment. A network operations center may use gateways to communicate with the satellite constellation. The satellite constellation may include sets of satellites with different orbits such as circular orbits with different inclinations, sets of satellites with elliptic orbits, sets of satellites with circular orbits of different altitudes including low earth orbits, medium earth orbits, and/or geosynchronous orbits, and/or sets of satellites with other orbits. The satellite orbits of the satellites in the satellite constellation may be selected to provide coverage to desired user population concentrations at different locations on the earth without using an excessive number of satellites.

This application claims the benefit of provisional patent applicationNo. 62/489,378, filed on Apr. 24, 2017, which is hereby incorporated byreference herein in its entirety.

FIELD

This disclosure relates generally to satellite communications, includingto constellations for satellite communications that include satelliteshaving different inclinations, e.g., to provide different coverage.

BACKGROUND

Communications systems often use satellites to convey data.Satellite-based systems allow information to be conveyed wirelessly overlarge distances, such as oceans. For example, satellite-based systemscan be used to convey information to land-based devices such as handheldequipment and home or office equipment. Further, satellitecommunications systems can be used to provide coverage where physicalinfrastructure has not been installed and/or to mobile devices that donot remain attached to an infrastructure resource.

It can be challenging to implement an effective satellite-basedcommunications system. If care is not taken, satellites may be deployedinefficiently, leading to elevated costs and suboptimal ground coverage.Further, if a satellite-based communications system is designed to servea period or region of highest demand, resources may remain idle duringperiods of lower demand and/or over regions with lower demand. Moreover,a conventional satellite-based communication system designed for aparticular demand level may not be able to dynamically increase capacityin response to higher demand.

SUMMARY

A satellite system may have a satellite constellation of communicationssatellites that provides services (e.g., voice and/or data services) toelectronic devices, such as portable electronic devices and home/officeequipment. A network operations center may use gateways to communicatewith the satellite constellation.

The satellite constellation may include sets of one or more satellites,with each set having different orbits. The satellite constellation may,as an example, include any/all of a set of satellites with circularorbits having different inclinations, a set of satellites with ellipticorbits, a set of satellites with circular orbits of different altitudesincluding low earth orbits (LEO) (of one or more different altitudes),medium earth orbits (MEO), and/or geosynchronous orbits (e.g., highlyinclined geosynchronous orbits), sun synchronous orbits and/or othersets of satellites.

The orbits of the satellites in the satellite constellation may beselected to enhance service efficiency. For example, one or more orbitsmay be selected to concentrate coverage over user population centers atvarious locations on the Earth. Additionally or alternatively, one ormore orbits may be selected to accommodate peaks in demand that coincidewith particular times of day. Such a design may help reduce the numberof satellites needed to provide a desired amount of coverage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents a diagram of an example communications system includingsatellites, in accordance with some embodiments.

FIG. 2 presents a schematic diagram showing an example of an electronicdevice in communication with a communications satellite, in accordancewith some embodiments.

FIG. 3 presents a diagram of illustrative satellite orbits around theEarth, in accordance with some embodiments.

FIG. 4 presents a diagram of the Earth and an associated inclinedsatellite orbit, in accordance with some embodiments.

FIG. 5 presents a graph in which coverage (e.g., probability density)for an illustrative satellite with an inclined orbit is plotted as afunction of latitude, in accordance with some embodiments.

FIG. 6 presents a diagram showing how user population density may varyas a function of latitude and may exhibit increased density (e.g.,peaks) and decreased density (e.g., valleys), and that shows how asatellite constellation may include satellite orbits with multipledifferent inclinations and other orbital attributes selected to matchsatellite coverage to user population density, in accordance with someembodiments.

DETAILED DESCRIPTION

The present disclosure, including the accompanying drawings, isillustrated by way of examples and not by way of limitation.

A communications network may include one or more communicationssatellites and other equipment, including ground-based communicationsequipment and user terminals (or user equipment (UE)). One or more ofthe satellites may be used to deliver wireless services, e.g., toportable electronic devices, home and/or office equipment, and otherequipment. For example, wireless services can be provided to handhelddevices, wearable devices, set-top boxes, media devices, mobileterminals, computing devices, sensors, etc. An illustrativecommunications system with satellites is shown in FIG. 1. As shown inFIG. 1, system 10 may include one or more constellations ofcommunications satellites 22. Satellites 22 may be placed in any/all oflow earth orbit (LEO) (e.g., at altitudes of 500-1500 km or othersuitable altitudes), geosynchronous orbit, and/or medium earth orbit(MEO) around the Earth 12. Satellites 22 may form a satelliteconstellation having one or more sets of satellites with different typesof orbits, e.g., that are synchronized with each other to provide userpopulations (or geographic regions) with desired amounts of coverage.There may be any suitable number of satellites 22 in the satelliteconstellation(s) of system 10 (e.g., 10-100, 1,000-10,000, more than100, more than 1000, fewer than 10,000, etc.).

Satellites 22 may deliver wireless services to equipment such aselectronic devices 18. Electronic devices 18 may include handhelddevices and/or other mobile devices, such as cellular telephones, tabletcomputers, laptop computers, wristwatches and other wearable devices,mobile terminals, drones, robots, and other portable electronic devices.Electronic devices 18 may also include stationary (or less portable)equipment, such as set-top boxes (e.g., satellite receivers), routers,home base stations, televisions, desktop computers, ground terminals(e.g., gateways), and other electronic equipment. Electronic devices 18may be located anywhere on or above the Earth, e.g., on land, at sea, orin the air. The services provided by satellites 22 may include telephone(voice) service, broadband internet access, media distribution servicessuch as satellite audio (satellite radio and/or streaming audioservices) and satellite television (video), data communications,location, and/or other services.

System 10 may include one or more network operations centers (NOCs) suchas NOC 16, which can be coupled to one or more gateways, e.g., gateways14 (sometimes referred to as ground stations). There may be any suitablenumber of gateways 14 in system 10 (e.g., 1-100, more than 10, more than100, fewer than 1000, etc.). Gateways 14 may have transceivers thatallow the gateways to transmit wireless signals to satellites 22 overwireless links 20 and that allow the gateways to receive wirelesssignals from satellites 22 over wireless links 20. Wireless links 20 mayalso be used to support communications between satellites 22 andelectronic devices 18. During media distribution operations, forexample, a gateway 14 may send traffic over an uplink (one of links 20)to a given satellite 22 that is then routed via a downlink (one of links20) to one or more electronic devices 18. Gateways 14 may perform avariety of services, including supplying media for electronic devices18, routing telephone calls (e.g., voice and/or video calls) betweenelectronic devices 18 and/or other equipment, providing electronicdevices 18 with internet access, and/or delivering other communicationsand/or data services to electronic devices 18. Gateways 14 maycommunicate with each other via satellites 22 and/or using ground-basedcommunications networks.

NOC 16 may be used to manage the operations of one or more gateways 14and/or the operations of one or more satellites 22. For example, NOC 16may monitor network performance and take appropriate corrective actionsif warranted. During these operations, NOC 16 may update software forone or more satellites 22 and/or electronic devices 18, may adjustsatellite 22 altitude and/or other orbital parameters, may direct one ormore satellites 22 to perform operations to adjust satellite solarpanels and/or other satellite components, and/or may otherwise controland maintain one or more of the satellites 22 in the constellation ofsatellites orbiting the Earth 12. Further, in some embodiments, NOC 16also may be configured to perform maintenance operations on one or moregateways 14.

Gateways 14, satellites 22, NOC 16, and electronic devices 18 may beconfigured to support encrypted communications. For example, NOC 16 andgateways 14 may communicate using encrypted communications. Similarly,gateways 14, satellites 22, and electronic devices 18 may communicateusing encrypted communications. This allows NOC 16 to issue securecommands and to receive secure information when communicating withgateways 14, satellites 22, and/or electronic devices 18. The use ofencrypted communications within system 10 also allows electronic devices18 to securely communicate with each other and with gateways 14, andalso allows gateways 14 to securely distribute media and/or otherinformation to electronic devices 18, e.g., in compliance with digitalprotection requirements.

During operation of system 10, satellites 22 may serve as orbiting relaystations. For example, when a gateway 14 transmits a wireless uplinksignal, one or more satellites 22 may forward these signals as downlinksignals to one or more electronic devices 18. In some embodiments, someelectronic devices 18 may be receive-only devices while other electronicdevices 18 may support bidirectional communications with satellites. Inscenarios in which an electronic device 18 supports bidirectionalcommunications, an electronic device 18 may transmit wireless signals toone or more satellites 22, so that the one or more satellites 22 mayrelay this information to one or more appropriate destinations (e.g.,gateways 14, other electronic devices 18, etc.).

Satellites 22 and links 20 may support any suitable satellitecommunications bands (e.g., IEEE bands), such as the L-band (1-2 GHz),S-band (2-4 GHz), C-band (4-8 GHz), Ka-band (27-40 GHz), V-band (40-75GHz), W-band (75-110 GHz), and/or other bands suitable for spacecommunications (e.g., frequencies above 1 GHz, below 110 GHz, and/orother suitable frequencies).

Some frequencies (e.g., C-band frequencies and other low frequenciessuch as L-band and S-band frequencies) may penetrate buildings and maytherefore be suitable for communicating with electronic devices locatedindoors at least some of the time, e.g., handheld electronic devices 18(e.g., devices that are mobile and that may sometimes be indoors and maysometimes be outdoors) and/or electronic devices 18 without an externalantenna/receiver. Other frequencies (e.g., V-band frequencies and otherhigh frequencies such as Ka-band and W-band frequencies) do not readily(or effectively) penetrate buildings and may therefore be suitable forcommunicating with electronic devices 18 that have an externalantenna/receiver or that are located outdoors and/or otherwise have aline-of-sight path to satellites 22. To accommodate a variety ofscenarios, e.g., both mobile device scenarios and home/office scenarios,satellites 22 may, for example, include C-band satellites (or other lowband satellites such as L-band or S-band satellites), V-band satellites(or other high band satellites such as Ka-band or W-band satellites)and/or dual-band satellites (e.g., satellites that that support C-bandand V-band communications or other low and high band communications).

In general, population density is not uniform and varies acrosslatitudes. However, satellite resources traditionally have beendistributed across latitudes without distinguishing between lesspopulated regions and more densely populated regions. As a result, aconstellation organized in such manner requires more satellites(vehicles) to provide coverage over populated areas—thereby providing asurplus of coverage over less densely populated areas. However,efficiencies can be achieved by dividing a constellation of satellitesinto groups of multiple sub-constellations, each with an inclination andquantity of satellites sized to provide the bulk of its coverage toareas in which the population (e.g., actual population and/or userpopulation) is dense. As a result, use of the constellation's resourcescan be enhanced as the number of satellites required to provide coverageand capacity is reduced, while excess capacity does not go unused overless populated areas. To ensure an efficient placement of on-orbitsatellites, the constellation design can be implemented to matchcoverage-density with population-density (either actual or user), asclosely as possible. For example, a geographic increase (e.g., peak) inpopulation-density (or other such metric) identifies a service area bylatitude. In at least some implementations, there can be multiple suchservice areas. Accordingly, a constellation can employ multiple sets ofsatellites with different orbital inclinations, e.g., Walker orbitinclinations, to approximate a match of coverage-density topopulation-density, facilitating an efficient placement of on-orbitsatellites.

FIG. 2 presents a schematic diagram of an illustrative electronic device18 in communication, over a wireless communications link 20, with anillustrative satellite 22. As shown in FIG. 2, electronic device 18 mayinclude one or more antennas 30. Antennas 30 may include monopoles,dipoles, and/or other types of antenna elements. Antennas 30 may, forexample, include loop antennas, helical antennas, patch antennas,inverted-F antennas, Yagi antennas, slot antennas, horn antennas, cavityantennas, dish antennas, arrays of antennas (e.g., a phased antennaarray that supports beam steering operations), or other suitableantennas. The antennas 30 can be implemented such that they are suitablefor communication with one or more satellites using one or moresatellite communications bands. Radio-frequency transceiver circuitry 32may include radio-frequency receiver circuitry and/or radio-frequencytransmitter circuitry that allows electronic device 18 to transmitand/or receive wireless signals over wireless communications link 20using one or more antennas 30. Electronic device 18 may also includecontrol circuitry 34 and input-output devices 36. Control circuitry 34may include storage, such as solid-state drives, random-access memory,and/or hard disk drives and other volatile and/or nonvolatile memory.Control circuitry 34 may also include one or more microcontrollers,microprocessors, digital signal processors, communications circuits withprocessors, application specific integrated circuits, programmable logicdevices, field programmable gate arrays, and/or other processingcircuitry. During operation, control circuitry 34 may run code(instructions) that is stored in the storage of control circuitry 34 toimplement desired functions for electronic device 18.

Control circuitry 34 may use input-output devices 36 to supply output toan interface configured to render output perceivable by a user and/or toexternal equipment, and may gather input received from a user and/orexternal source(s). Input-output devices 36 may include displaysconfigured to present images, audio devices (e.g., speakers and/ormicrophones), sensors, controls, and other components. For example,input-output devices 36 may include user input devices such as one ormore buttons, touch screens, sensors (e.g., accelerometers and/orgyroscopes), microphones for gathering voice commands, and/or othercomponents for gathering input from a user. Further, input-outputdevices 36 may include speakers, light-emitting components, displays,vibrators and/or other haptic output devices, and other equipment forsupplying a user with output. Input-output devices 36 may includesensors such as force sensors, position sensors, gyroscopes, magneticsensors, accelerometers, capacitive touch sensors, proximity sensors,ambient light sensors, temperature sensors, moisture sensors, gassensors, pressure sensors, and other sensors for gathering informationrepresentative of the environment in which electronic device 18 islocated.

A satellite, such as satellite 22, may include one or more antennas 40.Antennas 40 may be based on any suitable type(s) of antenna elements(e.g., antenna elements such as monopoles or dipoles, loop antennas,helical antennas, patch antennas, inverted-F antennas, Yagi antennas,slot antennas, horn antennas, cavity antennas, etc.). Antennas 40 may beused in any suitable type(s) of antenna arrays (e.g., phased antennaarrays, fixed direct radiating arrays, deployable direct radiatingantenna arrays, space fed arrays, reflector fed arrays, etc.). Theantennas 40 can be implemented such that they are suitable forcommunication with one or more electronic devices 18, gateways 14, orother communication devices/nodes using one or more satellitecommunications bands.

Satellite 22 may include transceiver circuitry that is communicativelycoupled (directly or indirectly) to antennas 40. The transceivercircuitry may include one or more components, such as one or moretransponders 42 for receiving uplink signals and transmitting downlinksignals, e.g., over links 20. Further, control circuitry 44 may be usedto control the operation of satellite 22. Control circuitry 44 mayinclude storage and/or processing circuits of the type used in controlcircuitry 34.

Power may be supplied to satellite 22 from power system 46. Power system46 may include one or more solar panels 48 (or arrays of solar panels)for converting energy from the sun into electrical power. Power system46 may include power regulator circuitry and batteries for storingelectrical power generated by solar panels 48, and for distributingpower to the components of satellite 22. Control circuitry 44 mayreceive information from one or more sensors 50. Further, controlcircuitry 44 may receive commands from NOC 16 and, using informationfrom one or more sensors and/or received commands, may performmaintenance and/or control operations (e.g., software updates,operations related to the deployment and operation of solar panels 48,diagnostic routines, altitude adjustments and other orbital adjustmentsusing propulsion system 52, etc.). Sensors 50 may include light-basedsensors (e.g., infrared cameras, visible light cameras, etc.), lidar,radar, sensors that measure backscattered light and/or backscatteredradio-frequency signals, temperature sensors, radiation sensors,accelerometers, gyroscopes, magnetic sensors, spectrometers, and/orother sensors. Sensors 50 may be used in performing remote sensingoperations, fault detection, satellite positioning, and otheroperations.

It may be desirable for the constellation of satellites 22 in system 10to include satellites with different types of orbits. As an example,satellites 22 may include orbits with different altitudes,eccentricities, inclinations, and other orbital attributes. One or moresun synchronous satellites (or a satellite in a sun synchronous orbit)may be included in the constellation of satellites 22 in system 10. Theone or more sun synchronous satellites can be configured to help meetdemand (e.g., as measured in throughput, the number of simultaneousconnections, or other such measures) during a high-demand period, suchas during an afternoon or evening period. By combining different orbitaltypes within the same satellite constellation, satellite resources canbe deployed with enhanced efficiency.

FIG. 3 is a diagram of two illustrative satellite orbits (geocentricorbits) about the Earth 12. Satellites 22 may orbit in a circular orbitas shown by illustrative circular orbit 56 or in an elliptic orbit suchas elliptic orbit 58. A circular orbit is characterized by aneccentricity of 0. An elliptical orbit has an eccentricity of greaterthan 0.

A satellite in a circular orbit may be characterized by an orbitalaltitude A, as shown in FIG. 3. Satellites 22 may orbit at any altitudesuitable for their intended purpose. For example, a satellite 22 mayorbit Earth 12 in low earth orbit (e.g., at an altitude A of 500-1500km), in geosynchronous orbit (at an altitude A of approximately 35,800km), or in medium earth orbit (e.g., between low earth orbit andgeosynchronous orbit). Examples of medium earth orbits includesemi-synchronous orbits and Molniya orbits. Semi-synchronous orbits havean altitude of about 20,000 km and are characterized by an orbitalperiod of one half of one sidereal day. A Molniya orbit has aneccentricity of greater than zero and a perigree location in theSouthern Hemisphere so a satellite in this type of orbit will spend mostof its orbital time above the Northern Hemisphere or vice versa. ATundra orbit is an elliptical orbit (with an eccentricity greater thanzero) that has twice the orbital period of a Molniya orbit. Otherelliptical orbits may be used, if desired (e.g., orbits witheccentricities of at least 0.3, at least 0.5, at least 0.7, less than0.8, etc.).

If desired, a satellite may have an inclined circular orbit (a circularorbit out of the equatorial plane). Consider, as an example, satellite22 of FIG. 4. In the diagram of FIG. 4, satellite 22 is orbiting aboutEarth 12 in satellite orbital plane SP. Plane SP is inclined atinclination (inclination angle) I with respect to equatorial plane EP,which is a plane that is aligned with the Earth's equator. Polar orbits(sometimes referred to as nearly polar orbits) are orbits that pass overthe north and south poles and are therefore characterized byinclinations of about 90° (e.g., at least 85°, at least 88°, at least89°, 90°, less than 90°, or other suitable polar orbit inclination).

One or more of satellites 22 in the satellite constellation of system 10may have a sun synchronous orbit. Sun synchronous orbits(heliosynchronous orbits) are polar orbits (near polar orbits) that passthe equator (or other given latitude) at the same local time each day.The altitude and inclination of a sun synchronous orbit are such thatthe nodal regression rate matches the Earth orbit rate. As a result, toa user on the ground, a sun synchronous satellite will pass overhead atthe same time of day each day. Because satellites with sun synchronousorbits are available to handle communications traffic at the same localtime each day, the inclusion of one or more sun synchronous satellitesin the satellite constellation of system 10 may help the satelliteconstellation to efficiently meet peak traffic demands.

In general, each type of orbit that is included in the satelliteconstellation of system 10 may help augment the performance of theconstellation in a different way. For example, an elliptic orbit such asMolniya or Tundra orbit may be used to provide capacity to a userpopulation center at a particular longitude and/or latitude (or range(s)thereof) in the Northern or Southern Hemisphere (e.g., a populationcenter in Europe, North America, Australia, or Asia). Further, sunsynchronous orbits may be used to provide capacity that is concentratedon one or more high-demand times of day (e.g., mornings or evenings).Inclined circular orbits may be used to provide coverage over a desiredrange of latitudes. Low-earth orbits may help reduce latency (e.g., fortraffic that involves voice telephone calls and other latency-sensitivetraffic) and may help reduce transmit and receive powers. Medium-earthorbits and geosynchronous orbits may help increase coverage, reducingthe total number of satellites needed to service a given region and maybe well suited to broadcast-type traffic (e.g., media distributionservices such as television services, music services, etc.).

Consider, as an example, a satellite with an inclined circular orbit. Anexample of the coverage (probability density) of a satellite with aninclination I as a function of latitude is illustrated in FIG. 5. Asillustrated in FIG. 5, coverage for an inclined orbit is concentratednear +I and −I. This attribute of an inclined orbit allows thecorresponding coverage to be selectively concentrated over one or morelatitudes, e.g., latitudes associated with increased demand, such asuser population centers (user traffic concentrations). By using sets ofsatellites, each of which is associated with a particular inclination,multiple areas of relatively higher demand (e.g., user populationcenters) at multiple respective different latitudes may be served. If,as an example, user populations are concentrated at latitudes of 55°,48°, 40°, and 33°, the satellite constellation of system 10 may includea first group of N1 satellites 22 with orbits having an inclination of55°, a second group of N2 satellites 22 with orbits having aninclination of 48°, a third group of N3 satellites 22 with orbits havingan inclination of 40°, and a fourth group of N4 satellites 22 withorbits having an inclination of 33°.

As illustrated by solid line 60 in the graph off FIG. 6, an exemplaryuser population density may be characterized by one or more peaks 64 andone or more valleys 66 at different latitudes. By adjusting the numbersof satellites at each corresponding inclination (e.g., the values of N1,N2, N3, and N4 in the preceding example), a satellite coverage(probability density) curve, such as dashed line curve 62 of FIG. 6 maybe produced that has one or more peaks 68 that partly or fully overlappeaks 64 and thereby help accommodate the variations in user populationdensity 60. By varying the numbers of satellites 22 with orbits at eachof multiple different inclinations, the total number of satellites 22may be reduced in the satellite constellation. If desired, efficiencymay be further enhanced by incorporating satellites with non-circularorbits, polar orbits such as sun synchronous orbits, medium earthorbits, and/or geosynchronous orbits into the satellite constellation.The use of a constellation that includes satellites with inclinedcircular orbits at multiple different inclinations is merelyillustrative.

Within the constellation of satellites 22 in system 10, each group ofsatellites 22 that share a common orbit (e.g., a common orbitalinclination and altitude for a set of low earth orbiting satellites withcircular orbits, a common elliptical orbital type for a set of mediumearth orbit satellites, a geocentric orbit, etc.), may include anysuitable number N of satellites 22. For example, N may be 1-100,10-1000, 10-10,000, 20-500, at least 10, at least 50, at least 100, atleast 200, fewer than 10,000, fewer than 1000, fewer than 500, fewerthan 100, or other suitable number.

Satellites 22 in the constellation of satellites may have the same typesof antenna arrays (with the same types of antenna elements), may havedifferent types of antennas (e.g., one type of antenna array may be usedfor low earth orbit satellites, another type of antenna array may beused for sun synchronous satellites, and another type of antenna arraymay be used for geosynchronous satellites), may have different types ofpower systems (e.g., different power sources, different numbers of solarpanels per satellite, etc.), or may have a common type of power system(e.g., a power system that has the same type and number of solar panels,etc.), may have different satellite buses or may share a commonsatellite bus architecture, may have different propulsion systems, mayshare a common type of propulsion system, etc. The satellites in thesatellite constellation of system 10 may be communications satellites(e.g., satellites that handle voice and data traffic, audio and/or videomedia broadcasts such as broadcasts of television traffic, and/or thathandle other suitable types of communications traffic). Different setsof satellites (having the same or different components) may havedifferent eccentricities, altitudes (e.g., different circular low earthorbit altitudes or other different circular orbit altitudes such aslower altitudes to minimize latency and higher altitudes to enhancecapacity by covering larger areas on the ground per satellite),inclinations, and/or other different orbital attributes. For example,one, two, three, four, or five or more sets of satellites may havecircular low earth orbits with different respective inclinations (e.g.,inclinations of 0-80°, 10-60°, 30-60°, more than 30° less than 80°, lessthan 60°, less than 70°, or other suitable inclinations) and one, two,three, four, or five or more of these orbits may have altitudes that areunder a given altitude, whereas one or more additional sets ofsatellites may have altitudes that are greater than the given altitude.If desired, one or more of these additional sets of satellites may begeosynchronous and one or more of these additional sets of satellitesmay be characterized by medium earth orbits. Geosynchronous orbits mayinclude inclined geosynchronous orbits (e.g., to enhance coverage athigher latitudes). One or more sets of satellites with one or moredifferent respective elliptic orbits (different respectiveeccentricities) may be included in the satellite constellation, ifdesired. Some of the satellites (e.g., satellites with inclinedgeosynchronous orbits or other orbits) may have storage that cachespopular media content (e.g., news headlines, popular media such aspopular movies, etc.). Satellites with cached content and/or othersatellites may multicast content (e.g., content may be transmitted tomultiple users in parallel). In some instances, content can be multicastaround the clock, while in other instances content can be multicastduring periods of low utilization, e.g., at night. In some instances,some content can be multicast for immediate consumption, while othercontent (e.g., applications, software updates, media content) can bemulticast for storage (e.g., for caching on devices, such as STBs orUEs), such this it is immediately available on demand.

In accordance with an embodiment, a satellite system is provided thatincludes a satellite constellation having at least first and second setsof communications satellites having different respective first andsecond orbital inclinations, gateways configured to communicate with thesatellite constellation, and a network operations center configured tocommunicate with the first and second sets of communications satellitesusing the gateways.

In accordance with another embodiment, the first and second sets ofcommunications satellites have low earth orbits.

In accordance with another embodiment, the low earth orbits of the firstand second sets of communications satellites have altitudes below afirst orbital altitude and the satellite constellation has at least athird set of communications satellites having a second orbital altitudethat is greater than the first orbital altitude.

In accordance with another embodiment, the third set of communicationssatellites includes geosynchronous satellites.

In accordance with another embodiment, the third set of communicationssatellites includes medium earth orbit satellites.

In accordance with another embodiment, the third set of communicationssatellites includes geosynchronous satellites with inclinedgeosynchronous orbits.

In accordance with another embodiment, the third set of communicationssatellites includes satellites with elliptical orbits that arecharacterized by an eccentricity of at least 0.7.

In accordance with another embodiment, the first set of satellites haslow earth orbits and includes satellites with a first altitude andsatellites with a second altitude that is different than the firstaltitude.

In accordance with another embodiment, the first and second sets ofcommunications satellites have low earth orbits with differentrespective altitudes below a first orbital altitude, the satelliteconstellation has at least a third set of communications satelliteshaving a second orbital altitude that is greater than the first orbitalaltitude, and the satellite constellation includes a fourth set ofcommunications satellites having a third orbital altitude that isgreater than the second orbital altitude.

In accordance with an embodiment, a satellite constellation is providedthat includes first, second, and third sets of communications satelliteseach with a different circular low earth orbit having a differentrespective orbital inclination, and a fourth set of communicationssatellites, the first, second, and third sets of communicationssatellites have orbital altitudes that are less than a first orbitalaltitude and the fourth set of communications satellites has a secondorbital altitude that is greater than the first orbital altitude.

In accordance with another embodiment, the fourth set of communicationssatellites includes geosynchronous satellites.

In accordance with another embodiment, the fourth set of communicationssatellites includes geosynchronous satellites with inclined orbits.

In accordance with another embodiment, the fourth set of communicationssatellites includes medium earth orbit satellites.

In accordance with another embodiment, the satellite constellationincludes a fifth set of communications satellites having inclinedgeosynchronous orbits.

In accordance with another embodiment, the satellite constellationincludes a fifth set of communications satellites each having an orbitalinclination greater than the orbital inclinations of the first, second,and third sets of communications satellites.

In accordance with another embodiment, the satellites constellationincludes at least one geosynchronous satellite.

In accordance with an embodiment, a satellite constellation is providedthat includes a first set of communications satellites in low earthorbit, each of the communications satellites in the first set ofcommunications satellites is characterized by an inclined circular orbitwith a first inclination and a second set of communications satellitesin low earth orbit, each of the communications satellites in the secondset of communications satellites is characterized by an inclinedcircular orbit with a second inclination that is different than thefirst inclination.

In accordance with another embodiment, each of the communicationssatellites in the first set of communications satellites has a firstantenna array formed from first antenna elements of a given type andeach of the communications satellites in the second set ofcommunications satellites has a second antenna array formed from secondantenna elements of the given type.

In accordance with another embodiment, communications satellites of thefirst and second sets of communications satellites each have a commonnumber of solar panels.

In accordance with another embodiment, the satellite constellationincludes a third set of communications satellites in low earth orbit,each of the communications satellites in the third set of communicationssatellites is characterized by an inclined circular orbit with a thirdinclination that is different than the first and second inclinations,and a fourth set of communications satellites in low earth orbit, whereeach of the communications satellites in the fourth set ofcommunications satellites is characterized by an inclined circular orbitwith a fourth inclination that is different than the first, second, andthird inclinations and the first, second, third, and fourth sets ofcommunications satellites are configured to communicate with a commonnetwork operations center.

The foregoing is merely illustrative and various modifications can bemade to the described embodiments. The foregoing embodiments may beimplemented individually or in any combination.

What is claimed is:
 1. A satellite system, comprising: a satelliteconstellation having at least first and second sets of communicationssatellites having different respective first and second orbitalinclinations and having a third set of communications satellitescomprising geosynchronous satellites with inclined geosynchronousorbits; gateways configured to communicate with the satelliteconstellation; and a network operations center configured to communicatewith the first, second, and third sets of communications satellitesusing the gateways.
 2. The satellite system defined in claim 1 whereinthe first and second sets of communications satellites have low earthorbits.
 3. The satellite system defined in claim 2 wherein the low earthorbits of the first and second sets of communications satellites havealtitudes below a first orbital altitude and wherein the satelliteconstellation has at least a fourth set of communications satelliteshaving a second orbital altitude that is greater than the first orbitalaltitude.
 4. The satellite system defined in claim 3 wherein thecommunications satellites of the fourth set of communications satelliteshave circular orbits.
 5. The satellite system defined in claim 3 whereinthe fourth set of communications satellites comprises medium earth orbitsatellites.
 6. The satellite system defined in claim 5, wherein thenetwork operations center is configured to communicate with the mediumearth orbit satellites using the gateways.
 7. The satellite systemdefined in claim 1 wherein the satellite constellation further comprisesa fourth set of communications satellites.
 8. The satellite systemdefined in claim 7 wherein the fourth set of communications satellitescomprises satellites with elliptical orbits that are characterized by aneccentricity of at least 0.7.
 9. The satellite system defined in claim 1wherein the first set of satellites has low earth orbits and includessatellites with a first altitude and satellites with a second altitudethat is different than the first altitude.
 10. The satellite systemdefined in claim 1 wherein the first and second sets of communicationssatellites have low earth orbits with different respective altitudesbelow a first orbital altitude, wherein the satellite constellation hasat least a fourth set of communications satellites having a secondorbital altitude that is greater than the first orbital altitude, andwherein the satellite constellation includes a fifth set ofcommunications satellites having a third orbital altitude that isgreater than the second orbital altitude.
 11. A satellite constellation,comprising: first, second, and third sets of communications satelliteseach with a different circular low earth orbit having a differentrespective orbital inclination; and a fourth set of communicationssatellites, wherein the first, second, and third sets of communicationssatellites have orbital altitudes that are less than a first orbitalaltitude, wherein the fourth set of communications satellites has asecond orbital altitude that is greater than the first orbital altitude,wherein the fourth set of communications satellites comprisesgeosynchronous satellites with inclined orbits, and wherein the first,second, third, and fourth sets of communications satellites areconfigured to communicate with a given network operations center usingat least one gateway.
 12. The satellite constellation defined in claim11 further comprising a fifth set of communications satellites, whereinthe fifth set of communications satellites comprises medium earth orbitsatellites.
 13. The satellite constellation defined in claim 11 furthercomprising a fifth set of communications satellites each having anorbital inclination greater than the orbital inclinations of the first,second, and third sets of communications satellites.
 14. A method ofoperating a satellite system having ground stations, a networkoperations center, and a satellite constellation having at least firstand second sets of communications satellites having different respectivefirst and second orbital inclinations and having a third set ofcommunications satellites comprising geosynchronous satellites withinclined geosynchronous orbits, the method comprising: with at least oneof the ground stations, communicating with the satellite constellation;and with the network operations center, communicating with the first,second, and third sets of communications satellites using the at leastone of the ground stations.
 15. The method defined in claim 14 whereinthe first and second sets of communications satellites have low earthorbits and wherein the method further comprises: with the at least oneof the ground stations, communicating with the first and second sets ofcommunications satellites having the low earth orbits.
 16. The methoddefined in claim 15 wherein the low earth orbits of the first and secondsets of communications satellites have altitudes below a first orbitalaltitude and wherein the satellite constellation has at least a fourthset of communications satellites having a second orbital altitude thatis greater than the first orbital altitude, the method furthercomprising: with the at least one of the ground stations, communicatingwith the fourth set of communications satellites.
 17. The method definedin claim 16 wherein the communications satellites of the fourth set ofcommunications satellites have circular orbits, the method furthercomprising: with the at least one of the ground stations, communicatingwith the communications satellites with circular orbits.
 18. The methoddefined in claim 16 wherein the communications satellites of the fourthset of communications satellites comprise medium earth orbit satellites,the method further comprising: with the at least one of the groundstations, communicating with the medium earth orbit satellites orbits.19. The method defined in claim 16 wherein the fourth set ofcommunications satellites comprises satellites with elliptical orbitsthat are characterized by an eccentricity of at least 0.7, the methodfurther comprising: with the at least one of the ground stations,communicating with the satellites with elliptical orbits.
 20. The methoddefined in claim 14 wherein the first and second sets of communicationssatellites have low earth orbits with different respective altitudesbelow a first orbital altitude, wherein the satellite constellation hasa fourth set of communications satellites having a second orbitalaltitude that is greater than the first orbital altitude, and whereinthe satellite constellation has a fifth set of communications satelliteshaving a third orbital altitude that is greater than the second orbitalaltitude, the method comprising: with the at least one of the groundstations, communicating with the fourth and fifth sets of communicationssatellites.